The invention relates to a method and a device for labeling flat mail items.
A problem associated with the processing of flat mail items, particularly letters, post cards, etc., in mail-routing facilities, is the fast and reliable application of labels to flat mail items. An example of this is automatic mail forwarding. In this case, the mail items are separated out for forwarding addressing, and re-addressed corresponding to predetermined data stored in a database. These items are provided with a label that covers both the old address and, possibly, a barcode applied to the surface of the item. The label is then provided a new barcode and the corresponding, new address. The label is applied in devices that are integrated into automatic letter-sorting facilities. The mail items processed by such sorting facilities vary in format, weight and thickness. In these facilities, the items are conveyed at speeds of, for example, 3.6 m/sec, which places stringent requirements on the speed at which the labels must be applied, as well as the exact positioning of the labels.
A device for contactless label application by means of suction air and compressed air is also known. In this device, the labels are unwound as a strip from a roll by a conveying device, and fed into the region of suction air and compressed air. A pneumatically-driven cutting blade executes a stroke, and a label is cut from the strip. An air nozzle blows the airborne label toward the vacuum chamber, where it remains in a waiting position. An approaching letter is recognized by a light barrier, and the vacuum chamber is switched to compressed air with the aid of a compressed-air valve. The label is then blown onto the surface of the letter. As soon as the label touches the letter surface, it is affixed. The compressed-air blast is selected to be strong enough to press the label firmly against the letter surface. The letter is transported further, and the feeding action of the device is subsequently re-initiated. A further label is then cut and moved into the waiting position (Standard Mobile Label Applicator Model 2111 from LABEL-AIRE).
A disadvantage of this device is that the mail items to be processed are not held securely in the labeling region, and must have the same thickness to assure precise positioning of the labels on the surface of the items.
U.S. Pat. No. 5,122,216 describes a method of applying labels to forms or mail items, in which rollers apply strips of adhesive to labels, which are in turn applied to the forms. Suction air and compressed air hold and apply the labels. With this solution, it is not possible to adapt to different mail-item sizes and label positions.
It is the object of the present invention to disclose a method and a device for applying labels to flat mail items, which offer precise label positioning on the items, a low susceptibility to breakdowns with a high throughput, and great flexibility in the processed label length.
In accordance with the invention, this object is accomplished by a device and method for labeling flat mail items which applies labels to the items by compressed air. The thickness and length of each item is determined in the time for initiating blowing of a respective label as a function of the length and thickness of the item and the desired position of the label on the item.
A particular advantage of the invention is a high precision in the positioning of the labels on the items, as well as reliable conveyance of the items, despite their varying thicknesses. A notable advantage of the use of carrier-free labels is the absence of waste material.